package/sconeserver: drop unrecognized options

package/sconeserver: drop unrecognized options

Drop Magick++-config, lettuce and ui options which are
not recognized since latest bump in commit
ca17e0c7a02298b0250cdc121bcacef0b58fffe1 (back in 2018).

Indeed:
- Magick++-config is not used since
  https://github.com/sconemad/sconeserver/commit/b025999b8a9a9715b72d0fc8ccbf0888e163388f
- Experimental UI and lettuce modules have been dropped since
  https://github.com/sconemad/sconeserver/commit/ccc1efdb8981fbef63a714ff6315c8a18372090a

Moreover, replace sconesite-image by image (broken since 2013 and
https://github.com/sconemad/sconeserver/commit/7693301fdb0076bf7676eb2db278c2f015ac7157)

As UI and lettuce options are broken since a long time, it does not seem
useful to add entries in Config.in.legacy

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>